Barrow's Scaly Bark-louse

Male of Lithoseopsis humphreysi, from Taylor (2013). As this specimen has been preserved in ethanol, most of the wings' scales have been washed off.

In yesterday's post, I told you about our project's new book on the terrestrial invertebrates of Barrow Island. In this post, I want to tell you about my own main contribution: a description of Barrow Island's resident species of Amphientomidae.

Amphientomidae is a family of the bark-lice, the Psocodea (or Psocoptera, perhaps). They differ from most other bark-lice in having the wings densely covered in scales, like the wings of a moth; someone on BugGuide once referred to an amphientomid as a "moth-hopper-louse-bug thingy". These scales are often arranged into striking patterns of contrasting colours (take a look at the individual below). When the late Courtenay Smithers initially identified our collections of bark-lice from Barrow Island (which we briefly reviewed last year, though most are still not identified to formal species), he highlighted the presence of an amphientomid in the collection as particularly interesting. Amphientomids are incredibly little known in Australia. Only three Australian species had previously been described, and all three were only known from a single specimen. The description in my paper is drawn from six specimens, so it represents a tripling of Australia's published tally!

A North American species of Lithoseopsis, L. hellmani, photographed by Diane Young.

With this in mind, a description of the Barrow Island amphientomid seemed in order. This, of course, required comparing it to the already-described Australian species, which had thankfully been given detailed descriptions (Smithers 1989; New 1994). Two of these were from Western Australia: one from the Kimberley region in the far north, the other from the Cape Range which is on the mainland close to Barrow Island. Both of these had been placed in the genus Seopsis, which is otherwise known from Africa and Asia. However, when I compared the Barrow Island specimens to descriptions of Seopsis and other Asian genera, things didn't quite add up. For instance, take a look at the face of the Barrow Island species:

In particular, note the position of the ocelli (the three simple eyespots) at the front of the face. In all the Australian species, these are widely spaced, and the two lateral ocelli are right alongside the compound eyes. In contrast, here is the face of a Japanese amphientomid:

The individual in this photo, from here, isn't identified but may belong to Paramphientomum yumyum (yes, really, that's its name). Note how in this species, all three ocelli form a close triangle in the centre of the face; Seopsis also has this arrangement of ocelli. Other features such as genital morphology were also inconsistent between the Western Australian species and Seopsis.

Instead, the Western Australian species are better placed in a genus called Lithoseopsis*. The Barrow Island specimens I assigned to the same species that had earlier been described from the Cape Range, Lithoseopsis humphreysi. There are some minor differences between the Barrow specimens and the Cape Range holotype, but with only one specimen available from the latter locality I couldn't really assess whether these were indicative of more than one species. The recognition of this species as Lithoseopsis is interesting, as this genus is otherwise known only from southern North America. How such an oddly disjunct distribution may have come about I have no idea; my first guess would be that it's somehow relictual. However, it's also worth pointing out that there are three other genera very similar to Lithoseopsis that share its broadly-spaced ocelli: the African genus Hemiseopsis and the circum-Mediterranean genera Marcenendius and Nephax. The relationship between these genera really deserves a proper study.

*And here's a bit of a cautionary tale for you all. When I initially submitted the manuscript of this paper for review, one of the reviewers pointed out that the Western Australian species shouldn't be placed in Lithoseopsis due to the absence of one of that genus' primary features, a sclerotised plate on the back of the abdomen. Therefore, the manuscript was revised and accepted to establish the WA species as a new genus. At this point, I should note, the only amphientomids that had been available from Barrow Island were males. However, shortly before the book was due to be published, I finally received a female specimen. This specimen possessed the sclerotised plate that had been absent in the males! The paper was quickly revised at the last minute to return the WA species to Lithoseopsis. The ability to examine a female from Barrow also lead me to change my mind about whether the Barrow species was distinct from the Cape Range species, represented only by a female holotype. Unfortunately, once the book had been published and I could see the final product, I found that I had missed correcting the genus and species name in the figure captions! Much wailing and gnashing of teeth immediately commenced, I can bloody well tell you. After the whole pureora/pureroa thing, 2013 has not made me look good as a proof-reader.

The Barrow Island specimens also tell us something interesting about intra-specific variation in amphientomids. A common feature of bark-lice is variation within species of wing development: individuals of a single species may have the wings fully developed, reduced or absent. In amphientomids, however, such variation has been rarely recorded. A couple of species are known in which males and females differed in wing development, but so far as was known all males and all females had wings the same size. In the Barrow Island specimens, however, some males had both pairs of wings large and fully developed, but others had the forewings slightly shortened and the hind wings reduced to minute flaps. As the reduced-wing specimens were otherwise little different from the fully-winged specimens, they seem unlikely to represent different species. Instead, Lithoseopsis humphreysi is the first recorded example for amphientomids of wing polymorphism within a single sex.

REFERENCES

New, T. R. 1994. A second species of Amphientomidae (Insecta: Psocoptera) from Western Australia. Proceedings of the Linnean Society of New South Wales 114 (4): 233–236.

Smithers, C. N. 1989. Two new species of Amphientomidae (Insecta: Psocoptera), the first record of the family for Australia. Proceedings of the Linnean Society of New South Wales 111 (1): 31–35.

Taylor, C. K. 2013. The genus Lithoseopsis (Psocodea: Amphientomidae) in the Western Australian fauna, with description of the male of Lithoseopsis humphreysi from Barrow Island. Records of the Western Australian Museum Supplement 83: 245-252.